Keep adding powder until it blows up, and then you will know the limit of the GP-100. Keep track of your data so you know when and how much powder it took to do so and adjust from there.
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Yeah, the .357 mag is fairly uneventful, in MY opinion. That is why I bought a 44 mag. That took me to the next level. That, too, became unevenful. Then I bought a 454 casull. Now I was getting somewhere. I pushed that gun to the max loads and yearned for more performance. Then came the 500 SW mag. This is about all I want. I am pretty happy with it.

The moral of the story is: Don't blow up your gun trying to achieve a performance level out of it's league. Buy a bigger gun!

Of course it is true that shooting hot loads will wear out a gun faster than shooting warm loads. And it is also true that shooting warm loads will wear out a gun faster than shooting "mouse-fart" loads. But, those are not SAFETY issues.

People bought .357 Magnums on medium frames like the GP-100 because of the compromise they provide between carry weight, power and trajectory. It once was a good and popular compromise. SAAMI's new standard that is down-grading its maximum potential has created issues in a lot of areas. As one example, Maryland requires a muzzle energy of 700 foot-pounds and a 6" barrel as the minimum legal deer load for a handgun. That was based on the specifications of the .357 Magnum, as advertized at the time that law was passed. Now, only Buffalo Bore and Grizzly load "factory" ammo that meets that specification.

Is it going to blow-up your GP-100 to shoot those rounds? No. Will it wear out your barrel faster? Yes. Does that mean that you should NEVER shoot those loads? No. Then what does it mean? As always, it means that you can safely shoot enough of those loads to sight-in your gun and hunt deer successfully without wearing out your gun, but if you choose to practice with those loads extensively, you WILL wear out your gun. And, shooting enough to safely work-up those loads is just more wear. So, if you are only going to use such powerful rounds for limited purposes, it may pay to BUY these hot loads instead of working them up as handloads.

One thing to be aware of when using the hottest loads in a revolver is that the actual velocity of those loads will decrease as the barrel wears. Losses of as much as 200 fps are documented between when the SAME gun was new and after it had been fired extensively, using the SAME loads. And, no, adding more powder to get that lost velocity back is NOT a safe practice.

But, I still blame SAAMI for creating the situation where a cartridge that was designed to produce 1500 fps with a 158 grain bullet from a 8-3/8" barrel...

It is my understanding that those figures were obtained with a 15" unvented test barrel, NOT an actual 8-3/8" revolver.

Yes, there have been some cases where loads have been made more mild, but a lot of what people perceive to be lighter loadings today are simply the result of the fact that once chronographs became inexpensive, it became impossible for manufacturers to make, shall we say, "highly optimistic" velocity claims.

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Of course it is true that shooting hot loads will wear out a gun faster than shooting warm loads. And it is also true that shooting warm loads will wear out a gun faster than shooting "mouse-fart" loads. But, those are not SAFETY issues.

That's correct. Unless you exceed the strength of the gun with a load that generates too much pressure, the wear from shooting is primarily from recoil--parts being banged together as the gun jumps around in recoil. The more recoil, the harder the parts get banged together.

However, at some point, going lighter on the loads isn't going to help much because of the fatigue properties of steel. In other words, moderate loads may not really shorten the life of a well-designed gun compared to really light loads because the gun is designed to tolerate moderate loads indefinitely. That's not to say it won't wear out. It will still wear out from the wear of internal parts, etc. but lightening recoil past a certain point won't affect that.

So is it OK for a gun to wear out eventually? (rhetorical question) The alternative is to not shoot it.

The guns I shoot often are treated as tools, cared for but well used.

However, I don't use screwdrivers as prybars. I understand that a Ruger is cheap to replace, not like the OP is wanting them for a $1500 Python but if your going for "beyond published" why not get a Contender? Not only would it cost about the same but, It will last forever with hot 357's. Heck you could get really impressive numbers if you also had a 357 Max barrel.

45 colt is a lot like 45-70, old low pressure round that can be loaded much "hotter" in stronger firearms than once offered. A 45-70 in a ruger #1 for example can be loaded close to 458 win mag...a lot like my "357 in a contender" suggestion.

The original Contenders are not really as strong as the old literature supposes. Many people have stretched those thin frame sides and/or widened the hinge pin hole using very hot loads or powerful wildcats. The G2 is much stronger. the Encore is stronger, still.

And, the "wear" from hot loads in revolvers is more than just loosening parts by banging them around with the recoil. With high pressure comes high temperature, and with that comes forcing cone erosion. That is most likely the cause for the significant velocity loss that comes from shooting too many hot loads.

As for H-110/WW-296, in 1980, Winchester gave the max load in Winchester cases with Winchester magnum primers and an unspecified 158 grain jacketed bullet as 16.6 grains, with a pressure of 39,500 CUP and a velocity of 1610 fps from a 8-3/8" SAAMI test barrel. I don't think that load changed while Winchester was marketing 296. Their manual said to NOT REDUCE those loads at all, so that is what I shot. Hodgdon's 2006 load pamphlet gave 16.7 grains as max for H-110 under a 158 grain XTP, with a pressure of 40,700 CUP and a velocity of 1561 fps out of a 10" test barrel. Cases and primers were also Winchester. Both are well under the CUP standard of 46,000 CUP, but will be over the psi standard of 35,000 psi, although it is generally recognized that pressures measured in CUP with a copper crusher are numerically lower than if they had been measured in psi with a piezoelectric transducer. And, strangely, it is now OK to reduce those loads to reach the 35,000 psi standard, and to go even 3% below that.

Those velocities illustrate that it is hard to explain velocities in manuals. Both velocities are from the test barrels rather than from the same loads in a commercially available "example" revolver (as is often done to give more realistic velocity expectations), and neither barrel was vented. Yet the bigger load with the higher pressure gave a lower velocity from the longer barrel. Go figure!

As for H-110/WW-296, in 1980, Winchester gave the max load in Winchester cases with Winchester magnum primers and an unspecified 158 grain jacketed bullet as 16.6 grains, with a pressure of 39,500 CUP and a velocity of 1610 fps from a 8-3/8" SAAMI test barrel.

I gotta believe that velocity figure is very optimistic.

www.handloads.com lists a loading with an unspecified 158gr JHP in front of 16.5gr W296, in a 6.5" barrel revolver and reports 1338fps muzzle velocity. That sounds a lot more realistic.

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With high pressure comes high temperature, and with that comes forcing cone erosion.

While that's certainly true, most folks don't consider a gun worn out because the barrel needs to be replaced.

As I stated in my post about WW-296, the data from Winchester and Hodgdon are from UNVENTED TEST BARRELS, so of course they are higher than velocities from revolvers. Besides the lack of vents to simulate the cylinder-to-barrel gap, these test barrels are also built to SAAMI minimum specifications, which is intended to maximize pressure, and that also maximizes velocity for the same load. The remarkable thing about these data is that they were BOTH test barrels, so you would think that results should be pretty close. But, of course, they were probably different lots of powder and primers, so that could easily make the difference seen.

Many manuals do not report the velocities from the test barrels. Instead, after working-up a maximum load in their test barrel, they fire it in a gun you can buy at your local gun shot to give a more realistic expectation of the velocity that a handloader is likely to achieve. For comparison, look at the table on page 771 of Speer Manual #14. It lists velocities of the same loads when fired from 30 guns chambered in .357 magnum, plus a test barrel. The test barrel was 10" long, so I will compare it to the Contender with 10" barrel. For their 158 grain bullet load, the test barrel produced 1591 fps and the contender produced 1587 fps. So, it seems like a Contender will produce velocities similar to a test barrel. On the other hand, a Ruger Blackhawk with a 10" barrel is listed as producing only 1365 fps with that load. And, in fairness, the way a revolver barrel is measured (not counting the chamber) makes that really a 11.65" barrel. Counting the cylinder length, the S&W M27 revolver with the 8-3/8" barrel is closer in length to the 10" test barrel, and it produced only 1221 fps. So, yes, test barrel velocities are quite optimistic with respect to velocities from revolvers.

And, revolver velocities also vary substantially for the same barrel length, even when made by the same manufacturer. That table in the Speer manual lists velocities from 9 revolvers with 6" barrels. For the same load withthe 158 grain bullet, the velocities range from 1080 fps to 1284 fps. Among 3 S&W M19s the range was from 1154 to 1284 fps, and for 2 S&W M28s it was 1080 to 1178 fps. In fact, the velocity from the revolver with the 8-3/8" barrel was beaten by an S&W of the same model and a Ruger, both with with 6-1/2" barrels, and 2 of the 9 revolvers with the 6" barrels.

That showes how poorly the published velocities in reloading manuals may match YOUR PARTICULAR revolver, and why you might exceed the velocities shown in the manuals for "example" guns (rather than test barrels) without exceeding the listed max charge weight or the actual pressure limit.

One more point. I have an old Lyman manual from the days when the loads were NOT pressure tested. (They were worked-up by those "dubious methods" looking for pressure signs.) But, they did use chronographs to provide velocities from their "example" guns. They also fired factory ammo and measured its velocity to obtain a goal for their "factory duplication load." For the .357 Magnum with 158 grain (lead w/GC) bullet, they obtained 1388 fps from a S&W M27 with 5" barrel using factory ammo. That is 674 foot-pounds. So, shooting the same load from a 6" barrel does not seem to be much of a leap to reach 1412 fps and 700 foot-pounds. And, even today, Buffalo Bore loads ammo to that energy level from a real revolver, as shown on their website.

However, the "factory duplication load" in that old Lyman manual used Herco powder, for some reason. And, it must have been WAY over SAAMI pressure limits of any day. My QuickLOAD program gives 70,000 psi with their load using default parameters and showes a 21% compression. Even enlarging the case volume to what my Security Six produces, I still get a lot of compression and over 60,000 psi. Apparently, Lyman actually shot those loads in their M27 without producing effects that deterred them from publishing that load in 1967. But, I am NOT going to publish it HERE,

The original Contenders are not really as strong as the old literature supposes. Many people have stretched those thin frame sides and/or widened the hinge pin hole using very hot loads or powerful wildcats. The G2 is much stronger. the Encore is stronger, still.

They are not as strong as a G2 but in all of the rounds they are chambered for (many being centerfire rifle rounds originally) I have never heard of one getting damaged by a 357mag.

But, I still blame SAAMI for creating the situation where a cartridge that was designed to produce 1500 fps with a 158 grain bullet from a 8-3/8" barrel is now not able to produce more than 1250 fps from a 6" barrel.

This quote is in error 2 ways.

First of all, it's not really accurate to say that the "cartridge was designed to produce 1500fps with a 158grain bullet" because it never really did that except with long unvented test barrels. I pointed that out and you brought up the WW-296 load as an example of why it really was designed to make 1500fps with a 158grain bullet. HOWEVER, it turns out that the velocity figure you listed as evidence was STILL from a test barrel and, when shot through a typical 6" barrelled revolver it shot nearly 300fps slower (doesn't make 1500fps) per the test data on handloads.com.

Second it's not really accurate to say that it won't produce more than 1250fps from a 6" barrel because the load you listed actually produced over 1300fps from a 6" barreled revolver, again as listed on handloads.com.

So when I objected to your comment, you provided, in return, a lengthy (correct) explanation of why it's reasonable to expect that velocities in long unvented barrels will be a lot higher than what is seen in reasonable length barrels with actual cylinder gaps. I understand everything in your explanation and while it's correct, it doesn't change the fact remains that the numbers you tried to use as "evidence" to support your original statement that I objected to (i.e. The .357Mag was designed to produce 1500fps/158gr in a typical revolver but SAAMI changed things so that it won't do that any longer), don't support that claim.

While you may feel it's reasonable to blame SAAMI, it's quite clear that SAAMI doesn't have anything to do with why a load that shoots over 1600fps in a long unvented test barrel shoots about 300fps slower in a 6" barreled revolver.

I'm not sure who is really the one shooting at a moving target. And, I am not trying to pick an argument.

But, I stand-by my comments that SAAMI has seriously down-graded the .357 and .44 magnum rounds with their new psi standard, as compared to their older CUP standard. And, I stand by my comments that has invited people who have strong guns to try to exceed the lower velocities of the newer standard. That is why I pointed the OP to pressure tested data from the old CUP standard, because I think that is a safe way to up the performance, and still stay within SAAMI standards, because CUP is STILL an accepted standard. I want to discourage "winging it" without pressure tested data as a guide.

Trying to compare apples to apples, the new Speer manual (#14) lists the maximum load of 296 as 14.7 grains to comply with the 35,000 psi standard, and says that achieves 1185 fps. It also lists 15.5 grains of (supposedly identical) H-110 as max and say that gives 1217 psi. Both velocities are from a S&W M19 with a six inch barrel. Compare that to Winchester's original load of 16.6 grains of 296 that produced only about 40,000 CUP, or Speer, Hodgdon, Hornady and Sierra pressure-tested loads from the 1980's that range all the way up to 17.8 grains and were supposed to be within the 46,000 CUP limit. OBVIOUSLY, the psi standard produces a much lower actual pressure than the CUP standard. Don't you agree with that?

Now, comparing velocities is more of a problem keeping apples to apples, because of the wide range of velocities that can occur with different guns shooting the same load and the same gun shooting the same amount of the same powder under the same bullet, but with different powder, primer and case lot numbers.

I don't have any velocity measurements from .357 ammo manufactured in the 1930s/40s and shot in any 8-3/8" barreled revolvers. But, I do have some fired cases with LARGE pistol primers from that era. So, I expect that things were probably pretty hot in those days. But, I do not really have a way of knowing just how close some of the original factory ammo got to their advertized velocities in real guns.

I do know that MODERN 10" test barrel data EXCEEDED that advertized velocity at pressures that are probably considerably lower than the old factory ammo. And, I see that there is still a Lyman load for a CAST LEAD 158 grain bullet that gets 1450 to 1460 fps with pressures around 42,000 CUP from a 4" VENTED test barrel. So even going to 46,000 CUP and an 8-3/8" vented test barrel seems to put 1500 fps within plausible reach. And, if you go here http://www.buffalobore.com/index.php...t_detail&p=100 you will see that Buffalo Bore lists velocities of 1485 and 1457 fps for their 158 grain JHP from revolvers with a 4" and 5" barrel, respectively. So, again, I don't see that the pre-WWII ammo had to surely be less than 1500 fps with LEAD bullets. If there is really an apples to oranges problem with the comparison of the old advertizing to the new manual velocities, it is partly that the original loads were lead, while most of todays manuals are giving data for jacketed bullets.

But, getting back to whether we are arguing or not, you seem to have picked on a minor detail in what I said about the design velocity of the original cartridge as a way of disagreeing with or changing the subject from my main point that the SAAMI psi standard has seriously downgraded the older magnum rounds from what they were under the CUP standard. You and some of the other posters also seem to be ignoring my secondary point that some of the old advertizing (and possibly old testing results) have been incorporated into regulations on the use of handguns that we must still obey, today, if we intend to use the .357 magnum cartridge for the uses that those regulations INTENDED it to be used for.

I think those points explain why we see so many people wanting to push .357 Magnum loads instead of going out to buy newer, heavier guns chambered in newer cartridges. And, I don't think posts that say the answer is to never shoot maximum loads in your .357 Magnum are going to be effective in stopping those people from seeking hot loads. I think our answers are better directed at getting that type of poster to look for hot PRESSURE-TESTED data and stay within that, with some warnings about what people should ALWAYS think about whenever they are approaching max loads. (As an aside, some of the max load data for the .357 magnum seems to use more powder than I have found will even fit into the case under the bullet used in the data, so there are obviously some issues to consider when trying to use that data.)

I don't have any velocity measurements from .357 ammo manufactured in the 1930s/40s and shot in any 8-3/8" barreled revolvers.

That test has actually been done.

Handloading resources may have reduced their maximum loads over time due to concerns about liability and as new technical data has come to light, but Handguns Magazine ran an article in the August/September 2006 issue in which they tested some vintage ammunition (.38spl and .357Mag) vs modern ammo. The specs were very similar, no evidence that the modern stuff was watered down.

The apparent slow reduction in velocity began in 1977 when SAAMI put pressure push the ammunition companies to publish velocity figures for .38spl and .357Mag ammunition based on chrono information from 4" Vented test barrels instead of data measured using the longer unvented test barrels that were common before that time. As the different companies came into compliance over a period of years, the appearance was that the ammunition was slowly being reduced in power. In reality, there was no reduction in power, only a change in the testing procedure, and the change happened abruptly for each company. It's just that the companies didn't all comply at the same time.

In addition, the change from CUP to PSI muddied the water even more.

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OBVIOUSLY, the psi standard produces a much lower actual pressure than the CUP standard. Don't you agree with that?

Attempting to compare CUP and PSI numbers is very complicated because they don't actually measure the same thing. PSI provides an actual peak pressure measurement while CUP provides information about the area under the entire pressure vs. time curve.

There's not a conversion between CUP and PSI that can be applied accurately in the general case. It's not even universally true that one number will always be higher than the other for a given cartridge. Trying to compare pressure specs in CUP to pressure specs in PSI to make a case that SAAMI is progressively reducing the maximum pressure specs is not as simple as it seems. Here's some reading on CUP and PSI.

From what I've seen, besides the fact that handloading resources (as opposed to SAAMI) may be becoming more conservative, the main reason that people believe that ammo power is being reduced comes from the fact that in the late '70s and early '80s the ammo industry gradually began publishing more realistic velocity figures.

Getting back to the original subject, it is wise to stick to published reloading data. Going back to vintage reloading manuals to find hotter loads isn't as safe as it might seem. There's likely a very good technical reason that the new data is different.

The troubles with trying to make an equation to convert CUP to psi is IRRELEVANT to my point and the evidence supporting it.

The data that produced CUP results at the 46,000 CUP SAAMI limit CLEARLY showes higher powder charge weights than the data that showes psi results at the 35,000 psi SAAMI limit. So, whatever the REAL peak pressures are, they are lower when meeting the psi limit than when meeting the CUP limit with the same powder.

The companies that actually operate both types of pressure measurement systems understand that. I have never heard any of THEM say that they actually measured the same load with both systems and found that that the .357 ammo that reached the psi limit was as powerful as the ammo that reached the CUP limit. In fact, some have said that they shot their NEW .357 Magnum data with the CUP system, DESPITE having the psi system available to use. Usually, that is powder vendors who do that, and the reason is left unstated, but obvious: if they use the psi system, their powders will appear less powerful than the powders of their competitors who choose to use the CUP system, and that would be bad for business. Also note that this means that not all CUP data is "old" data.

Saying "it ain't so" and using the variations in the pressure measurements, powder lot burn rates, etc. etc. to muddy the waters for makng comparisons may delude some, but most of us that have followed this for years are not confused by those arguments. And, I think that I have said enough that the other readers of this forum can make up their own minds.

As for the Handguns Magazine article, I did not read it, so I am not going to comment on its adequacy to make its point. I may try to find it later.

I will however point out that the industry has a habit of introducing new cartridges, adopting standards that make them look fantastic, loading some ammo to that level, then downloadng the commercial ammo later. One of the recent examples of that practice is the .454 Casull, which was given a 65,000 psi peak pressure spec by SAAMI, but for which commercial loads are usually restricted to 55,000 psi to avoid any problems.

I fully expect that S&W did the same with the .357 Magnum all those years ago.

But, that doesn't mean that they designed guns that would be unsafe with the ammo that reached the limit. The guns are supposed to be proofed with rounds that are 30% above the SAAMI limit, not 30% above whatever the ammo companies are currently loading below that limit. So, I still think that ammo that complies with the CUP limit is SAFE enough in modern guns that you are not going to hurt yourself by using it. And, I think that is SAAMI's position as well, since they still have the CUP standard as well as the psi standard. I think that puts me in good company as far as safety issues are concerned.

As for handloading to the CUP limit instead of the psi limit, it obviously needs to be done with care, and that is why I included some cautions. Many of the start loads under the CUP system are max loads under the psi system with this cartridge. So, if the psi system loads have left some people complacent with approaching max, they need to get a new perspective when using CUP data for the .357 Magnum.

The guns are supposed to be proofed with rounds that are 30% above the SAAMI limit, not 30% above whatever the ammo companies are currently loading below that limit.

I'm not aware of any standard under SAAMI that requires proofing with anything other than standard pressure loadings, I'd be very interested to see any information you have along those lines.

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So, I still think that ammo that complies with the CUP limit is SAFE enough in modern guns that you are not going to hurt yourself by using it.

I agree that if you're using ammo that complies with current SAAMI specs in modern firearms you shouldn't encounter problems.

That's not quite the same thing as saying that pressure limits, once published, are always good. It's important to understand that sometimes pressure specs are actually revised downward for safety reasons.

An interesting thread I happened upon. If you believe Iowegan, the .357Mag was revised downward by SAAMI in 1995. And again, if you believe him, it wasn't actually SAAMI's idea to do the revision.

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